fix(video): 修正默认码率配置并优化软件编码器

- 将默认码率从 8 Mbps 降至 1 Mbps，更适合嵌入式设备
- 修复 WebRtcConfig 中 max_bitrate < target_bitrate 的逻辑错误
- 优化 libx264/libx265 软件编码器的低延迟配置
- 优化 libvpx (VP8/VP9) 的实时编码参数

libs/hwcodec/src/ffmpeg_ram/mod.rs

@@ -119,14 +119,14 @@ impl CodecInfo {
     pub fn soft() -> CodecInfos {
         CodecInfos {
             h264: Some(CodecInfo {
-                name: "h264".to_owned(),
+                name: "libx264".to_owned(),
                 mc_name: Default::default(),
                 format: H264,
                 hwdevice: AV_HWDEVICE_TYPE_NONE,
                 priority: Priority::Soft as _,
             }),
             h265: Some(CodecInfo {
-                name: "hevc".to_owned(),
+                name: "libx265".to_owned(),
                 mc_name: Default::default(),
                 format: H265,
                 hwdevice: AV_HWDEVICE_TYPE_NONE,